Supercapacitors are becoming attractive power sources in memory backup devices, electric vehicles, military weapons, space equipment and in a number of day-to-day electronic equipment. Especially for military, space and electric vehicle applications, supercapacitors with high energy and power densities that can withstand harsh temperature environments are extremely desirable. A supercapacitor design for a specific application that requires high energy density or high power density or both, requires selecting proper electrode materials and a suitable electrolyte. Interface properties of the electrode/electrolyte, such as but not limited to the interface structure, charge transfer, ion diffusion, and the like, play a vital role in governing the rate capability and specific capacitance of the supercapacitor. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are useful techniques for characterizing such electrode/electrolyte properties in a supercapacitor assembly.